AMPTEC Research · Failsafe Ohmmeters
620ES
Mid-range digital failsafe ohmmeter for ultra-safe resistance testing of igniters and explosive components.
The Amptec 620ES is a mid-range digital failsafe ohmmeter for resistance testing on bridge wires, fuzes, flares and other explosive components. A built-in current-limiting resistor network keeps the test current at 8 mA or less under every condition, and the limit stays in force even if an internal part fails, so a fault leaves the meter safe rather than dangerous. Ordnance, aerospace and munitions labs use it for accurate resistance checks in flammable or volatile atmospheres. Evencat is the sole distributor for AMPTEC Research in Taiwan.
Overview
The 620ES covers 2 Ω to 200 KΩ, the span most igniter and explosive-component tests need. At its core is a failsafe current-limiting resistor network that keeps the test current on every range at 8 mA or less; a circuit fault causes the meter to fail safe rather than push more current into the device under test. Accuracy is ±.02% of reading plus ±.05% of range, read out on a 4 1/2 digit LED display that updates 3 times a second. The meter is approved by the USAF Non-Nuclear Munitions Safety Board for all non-nuclear munitions, complies with UL-913 and is built under ISO 9001:2015. The design has a long track record: units more than 20 years old are still in daily use. Before ordering, check whether you need the RS-232C interface or continuous isolated power for a fixed station, and whether the reversed-current option (RP1) is worth having for your lowest-resistance parts.
Key specifications
| Measurement range | 2 Ω to 200 KΩ |
|---|---|
| Nominal test current | 5 mA (2Ω and 20Ω ranges), 500 µA (200Ω range), 0.5 µA (200KΩ range) |
| Maximum failsafe current | 8 mA |
| Accuracy | ± .02% of reading + ± .05% of range |
| Resolution | 100 µΩ / 1 mΩ / 10 mΩ / 10 Ω (by range) |
| Display | 4 1/2 digit LED |
| Open-circuit voltage | 1.6 VDC |
| Maximum internal voltage | 4.8 VDC |
| Maximum input voltage | 250 VDC |
| Update rate | 3 readings/second |
| Power | 4 rechargeable 5AHr NICAD batteries |
| Operating temperature | 0° to 50° C |
Features
Failsafe current limiting
A built-in current-limiting resistor network keeps the test current at 8 mA or less; the limit stays in force even if an internal component fails, so a fault leaves the meter safe.
Accurate mid-range measurement
Ranges from 2 Ω to 200 KΩ with accuracy of ±.02% of reading plus ±.05% of range cover the resistance checks igniters and explosive components require.
4 1/2 digit LED display
A clear 4 1/2 digit LED readout updating 3 times a second gives an immediate, high-resolution resistance value.
Military and safety approvals
Approved by the USAF Non-Nuclear Munitions Safety Board for all non-nuclear munitions, UL-913 compliant and built under ISO 9001:2015.
Portable rechargeable power
Runs on 4 rechargeable 5AHr NICAD batteries and weighs only 3.5 lbs, so it serves field and lab work equally.
Proven durability
The rugged design has a long service record: units more than 20 years old are still working in the field.
Typical applications
Aerospace final assembly
Resistance verification of pyrotechnics before installation
On rocket and aircraft assembly lines, technicians measure bridge wire resistance before a squib is installed to confirm it meets the design specification. The 620ES failsafe circuit keeps the test current under 8mA, removing the risk of accidental ignition and letting engineers screen parts one by one on the assembly floor.
Munitions maintenance
Routine checks of explosive initiators in a munitions depot
Military ordnance maintainers survey stored initiators and flares on a schedule under MIL-STD-810F practice. The 620ES complies with UL-913 intrinsic safety, so it can be used directly in flammable and explosive environments, and its ±0.02% of reading accuracy separates good units from degraded ones without misjudgment.
Pre-launch testing
Firing circuit continuity confirmation at a launch site
During the countdown for a satellite or sounding rocket, ground support engineers confirm bridge wire resistance on every explosive bolt and separation device in the firing circuit before launch is authorized. With 3 readings a second and a 4 1/2 digit LED display, the 620ES lets them clear the whole circuit under time pressure, which is why NASA and the USAF have relied on it for so long.
Options and configuration
Tick the options you need. We compile the configuration into a list and carry it into the quote form.
Standard package (included)
Hardware options
Downloads
Need pricing, specifications or lead time for 620ES?
Also available for rent: 620ES is part of the AMPTEC rental program, for project peaks, calibration backup and pre-purchase trials. Rental inquiry →